"We found that areas of the country that had higher numbers of vascular surgeons had more bypass surgery performed and lower amputation rates," said principal investigator Vivian Ho, a health economist at Rice University's Baker Institute for Public Policy.

Amputation rates can vary as much as tenfold in different areas of the U.S., so Ho wanted to analyse whether the availability of vascular surgeons in a region affects revascularisation and amputation rates for patients with PAD. Collaborating with the University of Alabama in Birmingham and Intermountain Health Care in Salt Lake City, Utah, Ho identified all patients with PAD in the Medicare claims data in 1994 and tracked their claims through 1999. She separated data on more than 143,200 patients who survived through 1999 by hospital referral region and merged it with information on the supply of local physicians and vascular surgeons.

Ho's statistical analysis of the data revealed that a .30 increase in the number of vascular surgeons per 10,000 Medicare beneficiaries resulted in almost a 1 percent increase in bypass surgery rates and a 1.6 percent reduction in amputation rates. "Regional variability in specialists who treat PAD is influenced by factors other than regional medical needs," Ho stated.

Ho also studied the availability of interventional radiologists, who can perform angioplasty in the lower extremities of patients with PAD to improve circulation. "We found weaker evidence that greater availability of interventional radiologists increases angioplasty rates and reduces amputation rates," Ho said.

"What surprised me most about the study is the disparity in the supply of specialists and the fact that so much of the variation in the supply is determined by where the specialists want to live rather than where they are needed most," she said.